Phase 2 study of the efficacy and safety of erdafitinib in patients (pts) with intermediate-risk non–muscle-invasive bladder cancer (IR-NMIBC) with <i>FGFR3/2</i> alterations (alt) in THOR-2: Cohort 3 interim analysis.
Authors: Siamak Daneshmand, Renata Zaucha, Benjamin Adam Gartrell, Yair Lotan, Syed A. Hussain, Eugene K. Lee, Giuseppe Procopio, Fernando Galanternik, Vahid Naini, Jenna Carcione, Spyros Triantos, Mahadi Baig, Jodi K. Maranchie
Journal: Journal of Clinical Oncology (2023)

504 Background: Current treatments (tx) of papillary NMIBC are not selective. Novel tx can be assessed on measurable disease (eg, a marker lesion) to rapidly and directly assess antitumor efficacy. FGFR inhibitor therapy may improve outcomes for pts with IR-NMIBC with FGFR3/2alt. Erdafitinib (erda) is an oral selective pan-FGFR tyrosine kinase inhibitor approved for locally advanced or metastatic urothelial cancer in adults with FGFR3/2alt who have progressed during or following ≥1 line of platinum-containing chemotherapy. THOR-2 (NCT04172675) is a multicohort phase 2 study of erda in pts with NMIBC. We report results in an exploratory cohort of pts with IR-NMIBC with FGFRalt (Cohort 3). Methods: Inclusion: age ≥18 y, with histologically confirmed NMIBC with FGFR3/2alt (local/central testing) and recurrent IR disease, with all previous tumors being low grade (Gr) (Gr 1-2), Ta/T1, no previous carcinoma in situ, risk of progression &lt;5% in the next 2 y, and risk of recurrence &gt;50%. All tumors were removed by transurethral resection of bladder tumor except for a marker lesion (single untouched 5-10 mm lesion). Pts received continuous oral erda 6 mg once daily without uptitration in 28-d cycles. Urine cytology was performed at the time of complete response (CR). Pts with a partial response (PR) or CR ≤3 mos of starting erda continued erda for up to a maximum of 2 y, until progressive disease, intolerable toxicity, withdrawal of consent, investigator decision to discontinue tx, or study closure. Primary exploratory end point: CR rate (CR = disappearance of the marker lesion without any new lesions; if there is a remnant of the marker lesion, no viable tumor should be seen on histopathological examination); key secondary end point: safety. Results: As of the data cutoff (Sep 2022) (median follow-up of 6.2 mos), 10/11 enrolled pts have received erda (enrolled population; median age: 66 y [range 47-77]; 9 Ta, 2 not staged). Pts received erda for a median duration of 2.9 mos (range 1.1-8.4). Efficacy (n=8 evaluable): 6 pts had CR (CR rate, 75.0%; 95% CI, 34.9-96.8%), and 1 had PR. Of 7 pts with CR or PR, median observed duration of response was 2.8 mos. Safety (≥1 dose of erda; n=10): the most common tx-emergent adverse events (TEAEs) were hyperphosphatemia (90.0%; n=9), diarrhea (60.0%; n=6), dry mouth (50.0%; n=5), dry skin (30.0%; n=3), dysgeusia (30.0%; n=3), and constipation (30.0%; n=3). One pt had Gr ≥3 dysuria (10.0%) and 1 (10.0%) had Gr ≥3 tx-related diarrhea. One pt (10.0%) had Gr 1 tx-related central serous chorioretinopathy. No pts had tx-related serious TEAEs or tx-related TEAEs leading to discontinuation. No deaths occurred. Conclusions: Data from Cohort 3 of THOR-2 demonstrate efficacy in adult pts with IR-NMIBC with FGFRalt. Safety data were consistent with the known safety profile of erda. Clinical trial information: NCT04172675 .